Catalyst composition useful for preparing 2,6-xylenol

ABSTRACT

A process for preparing 2,6-xylenol in high selectivity and a catalyst composition useful therein are disclosed. The process comprises reacting phenol, o-cresol or mixtures thereof with methanol in presence of water, hydrogen and a catalyst consisting essentially of Fe 2  O 3 , SnO 2 , Cr 2  O 3 , and K 2  O.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 45,571, filedJune 4, 1979, now U.S. Pat. No. 4,227,024.

FIELD OF THE INVENTION

The invention is in the general field of processes for preparing2,6-xylenol by alkylation of phenol or o-cresol and a catalystcomposition useful therein.

GENERAL BACKGROUND

2,6-Xylenol is used to prepare polyphenylene oxide which has utility asan engineering plastic.

Many catalysts are known for the preparation of 2,6-xylenol by theortho-alkylation of phenol. For example, U.S. Pat. Nos. 3,972,836 and4,041,085 teach the use of magnesium oxide. German publication No.2,704,440 teaches the use of calcium oxide. German publication No.2,716,035 teaches the use of copper chromite alone or in combinationwith MnO, ZnO, Al₂ O₃, or MnO₂. U.S. Pat. No. 4,024,195 teaches the useof a combination of Fe₂ O₃ /SiO₂ /Cr₂ O₃ /K₂ O. U.S. Pat. No. 3,790,641teaches the use of the following oxide components: Mg-Ce-Sn-V; Ce-Sc-Sn;La-Y-Sn.

The MgO based catalysts have the disadvantage of requiring a hightemperature (e.g. 475°-525° C.): additionally, they have a lowerselectivity as compared to the catalyst used in the present invention.Iron oxide based catalysts alone have very low activity. Use of vanadiumoxide in combination with iron oxide improves the activity but resultsin high methanol decomposition. The Fe₂ O₃ /SiO₂ /Cr₂ O₃ /K₂ O catalystworks well but results in the formationof an undesirable amount of BTX(benzene, toluene, xylenes). The catalyst of my invention, as comparedto the aforementioned catalyst, has the advantage of having a higherselectivity in preparation of 2,6-xylenol and the production of lessBTX.

BRIEF SUMMARY OF THE INVENTION

In one aspect, the present invention is directed to a process forpreparing 2,6-xylenol in high selectivity by reacting phenol, o-cresol,or mixtures thereof, with methanol in the presence of water, and,optionally, hydrogen, using a catalyst consisting essentially of Fe₂ O₃,SnO₂, Cr₂ O₃ and K₂ O.

In another aspect, the present invention is directed to a catalystcomposition which consists essentially of a major amount of Fe₂ O₃ andminor amounts of SnO₂, Cr₂ O₃ and K₂ O.

DETAILED DESCRIPTION The Catalyst Composition

The catalyst composition of my invention contains a major amount of Fe₂O₃ and minor amounts of SnO₂, Cr₂ O₃ and K₂ O. Suitable and preferredamounts of the various components are shown in the following table, inweight percent.

    ______________________________________                                        Component      Suitable Preferred                                             ______________________________________                                        Fe.sub.2 O.sub.3                                                                             90-97    93-96                                                 snO.sub.2      0.5-5    1-3                                                   Cr.sub.2 O.sub.3                                                                             0.5-5    1-3                                                   K.sub.2 O      0.01-1   0.02-0.5                                              ______________________________________                                    

While the amounts shown in the table can provide totals above 100 it isto be understood that use of a larger amount of one or more componentswill require a lesser amount of the other components so that the totalamount is not above 100.

Knowing the various components used in the catalyst composition of myinvention any person skilled in the art, without undue experimentation,can readily prepare the composition. In order to provide a more completedisclosure a description will be provided of a typical means ofpreparing the composition.

Suitable materials for use in preparing the catalyst composition areshown below.

    ______________________________________                                        Component Source Acceptable                                                   ______________________________________                                        Fe.sub.2 O.sub.3                                                                        Ferric Nitrate - Fe(NO.sub.3).sub.3 . 9H.sub.2 O                              Ferric Sulfate - Fe.sub.2 (SO.sub.4).sub.3 . 9H.sub.2 O             SnO.sub.2 Tin (IV) Nitrate                                                              Tin (II) Acetate                                                              Tin (II) Chloride                                                             Tin (IV) Chloride                                                   Cr.sub.2 O.sub.3                                                                        Chromium Nitrate - Cr(NO.sub.3).sub.3 . 9H.sub.2 O                            Chromium Acetate - Cr(C.sub.2 H.sub.3 O.sub.2).sub.3 . H.sub.2                O                                                                             Chromium Oxalate - Cr.sub.2 (C.sub.2 O.sub.4).sub.3 . 6H.sub.2                O                                                                             Chromium Sulfate - Cr.sub.2 (SO.sub.4).sub.3 . 18H.sub.2 O                    Chromium Chloride - CrCl.sub.3 . 6H.sub.2 O                         K.sub.2 O KOH, K.sub.2 CO.sub.3, Potassium Acetate,                                     Potassium Oxalate                                                   ______________________________________                                    

The iron, chromium and tin components are dissolved in water(temperature can be 20°-90° C., but preferably is 60°-80° C.).Precipitation can be effected with ammonia, sodium carbonate or sodiumhydroxide. The precipitation step should be slow (requiring about 1hour). The precipitate should be aged at least 1 hour before filtrationand washing. It is then dried in air at 110°-180° C. The potassiumcomponent is then added, following which the composition is dried andcalcined at 470°-600° C. for 1 to 6 hours, preferably for 2-3 hours, atabout 500° C. The composition is then screened to a desirable mesh size(8-20 mesh).

When the catalyst is used in the process described herein it is placedin the reactor and reduced with hydrogen gas prior to use. The hydrogengas is passed over the catalyst at a temperature of 300° to 500° C. at aflow rate of 2 to 6 volumes of hydrogen per minute per volume of reactorfor 2 to 12 hours.

THE PROCESS

My process can use phenol, o-cresol or any range of mixtures thereof.Methanol is used in the process with a suitable amount being in therange of about 1 to about 10 moles of methanol per mole of phenol and/oro-cresol. On the same basis the preferred amount of methanol is in therange of about 3 to about 5.

The presence of water is desirable in conducting the process. A suitableamount of water is about 5 to about 15 weight percent, based on thetotal phenolics and methanol. On the same basis the amount of water isin the range of about 8 to about 12.

It is necessary that the catalyst be treated (i.e. reduced) withhydrogen prior to commencing the process. (This feature has beendescribed in connection with the description of the catalyst.) In somecases it may be desirable to use hydrogen as a co-feed in conducting theprocess. When hydrogen is used the amount is in the range of 0.5 to 10volumes per volume of catalyst per minute.

The amount of catalyst used is related to the liquid hourly spacevelocity as follows ##EQU1##

A suitable range of LHSV is about 0.1 to about 5, with the preferredrange being about 0.2-3.

The process is conducted at a temperature in the range of about 380° to420° C. (Above 420° C. methanol decomposition occurs). Preferably, thetemperature is in the range of about 400° to about 415° C.

The reaction is conducted at a pressure from atmospheric to 1,000 psig.Preferably, the pressure is not above 200 psig.

The desired product (i.e. 2,6-xylenol) can be recovered from thereaction products by fractional distillation.

The process of my invention results in a very high selectivity of2,6-xylenol. Of total alkylated aromatics in the product mixture, theo-cresol and 2,6-xylenol will be at least 99 weight percent. Majorimpurities are 2,4,6-trimethylphenol, 2,4-xylenol and BTX.

In order to illustrate the nature of the present invention still moreclearly the following examples will be given. It is to be understood,however, that the invention is not to be limited to the specificconditions or details set forth in these examples except insofar as suchlimitations are specified in the appended claims.

EXAMPLE 1

This example illustrates the preparation of the catalyst. 300 gFe(NO₃)₃.9H₂ O and 3 g Cr(NO₃)₃.9H₂ O were dissolved in 3000 ml H₂ O. 3g of Sn was dissolved in HNO₃ and added to the solution. The iron,chromium and tin oxides were precipitated at 25° C. with 20 percentaqueous ammonia to a pH value of 7.0. The precipitate was filtered,washed with water and dried overnight at 140° C. in air. K₂ CO₃ (17 mg)was added in 30 cc H₂ O and the material re-dryed at 140° C. It was thencalcined in an air atmosphere at 470° C. and crushed and sieved into an8×20 mesh fraction.

The catalyst had the following composition, in weight percent: Fe₂ O₃--94.8; SnO₂ --3; Cr₂ O₃ --2; K₂ O--0.2.

EXAMPLE 2

20 grams of the catalyst were placed in a 1/2 inch stainless steelreactor. Hydrogen gas was passed through the reactor at 370° C. at arate of 200 cc/min for 4 hours.

The feedstock in this example consisted of 1 part phenol, 1 parto-cresol, 2 parts methanol, and 0.2 part water (all by weight). Thefeedstock was pumped at LHSV=2 through a preheat section at 375° C. andthen through the catalyst bed controlled at 400°-410° C.

No plugging of the catalyst was observed.

A run was made on the reactor for 8 consecutive days for a total runtime of about 60 hours.

The product was analyzed by GLC.

The results are shown below in Tables I and II.

                  TABLE I                                                         ______________________________________                                                                     Cumulative                                       Product Analysis  60 Hours   0-60 Hours                                       ______________________________________                                        Methanol, weight %                                                                               8.30       9.36                                            H.sub.2 O, weight %*                                                                            20.96      20.72                                            Cresylics, weight %                                                                             70.74      69.92                                            ______________________________________                                         *Calculated-                                                             

                  TABLE II                                                        ______________________________________                                                        Weight Percent                                                Cresylics                    Cumulative                                       Distribution      60 Hours   0-60 Hours                                       ______________________________________                                        BTX*              0.15       0.16                                             Anisole           0.05       0.05                                             Phenol            5.07       7.35                                             o-Methylanisole   0.06       0.05                                             o-Cresol          34.19      38.24                                            2,6-Xylenol       59.97      53.69                                            2,4-Xylenol       0.06       0.05                                             2,4,6-TMP         0.41       0.39                                             High boilers      0.04       0.02                                                               100.00     100.00                                           ______________________________________                                         *Benzene toluene, xylenes                                                

Additional runs were made using the same conditions except for catalyst.The following catalysts were tested:

Combination of iron and copper

Combination of iron and copper chromite

Combination of iron and MnO₂

Combination of iron and CoO

Combination of iron and V₂ O₃

Combination of iron and MoO₃

All of the foregoing catalysts resulted in plugging of the catalyst.

A run was made using the following catalyst Fe₂ O₃ /SiO₂ /SnO₂ /K₂ O.The run had a low activity (2,6-xylenol formation) which decreasedrapidly.

Thus, having described the invention in detail, it will be understood bythose skilled in the art that certain variations and modifications maybe made without departing from the spirit and scope of the invention asdefined herein and in the appended claims.

I claim:
 1. A catalyst composition consisting essentially of thefollowing materials in percent by weight: Fe₂ O₃ --about 90 to about 97;SnO₂ --about 0.5 to about 5; Cr₂ O₃ --about 0.5 to about 5; K₂ O--about0.01 to about
 1. 2. The catalyst composition of claim 1 wherein thematerials are present in the following amounts: Fe₂ O₃ --about 93 toabout 96; SnO₂ --about 1 to about 3; Cr₂ O₃ --about 1 to about 3; K₂O--about 0.02 to about 0.5.
 3. The catalyst composition of claims 1 or 2characterized further in that it has been treated with hydrogen gas at300° to 500° C. for 2 to 12 hours at a flow rate of 2 to 6 volumes ofhydrogen per minute per volume of reactor.
 4. The catalyst compositionof claim 1 wherein the materials are present in the following amounts:Fe₂ O₃ --about 94.8; SnO₂ --about 3; Cr₂ O₃ --about 2; K₂ O--about 0.2.5. The catalyst composition of claim 4 characterized further in that ithas been treated with hydrogen gas at 370° C. for 4 hours at a rate of10 cc/min per gram of catalyst.